This invention relates to a circuit for selectively suppressing contour enhancement of an image which appears on a display screen owing to a video signal.
A conventional contour enhancement circuit comprises a circuit for subtracting a prescribed component of a video signal in between horizontal scanning intervals, and a circuit for adding a signal representing the result of subtraction to a prescribed component of the video signal. In general, therefore, contour enhancement using a white border is achieved if the result of subtraction is positive, and contour enhancement using a black border is performed if the result of subtraction is negative.
However, owing to the nature of human vision, a black border often is offensive to the eye. In particular, applying a black border to a red portion gives an unnatural appearance. For example, it would be unnatural for a black border to appear on the red lips of the human face.